fix: Fix autoloading issue in Client.php

Author: saygiselimts

src/Client.php

@@ -1,7 +1,10 @@
 <?php
 
+declare(strict_types=1);
+
 namespace COT;
 
+
 use Exception;
 use Firebase\JWT\ExpiredException;
 
@@ -17,7 +20,7 @@
 use COT\Util\JWTKUtils;
 use COT\Util\PKCEUtils;
 
-require '../vendor/autoload.php';
+require_once  __DIR__ . '../vendor/autoload.php';
 
 if (!defined('URL_REALM')) {
     define('URL_REALM', 'https://auth-qa.trustedshops.com/auth/realms/myTS-QA');